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July 12, 2011 -- Doctors could identify more patients who may benefit from aggressive cancer screening by updating family cancer histories every few years, new research finds.

Family history is among the most important determinants of cancer risk, and it is used to identify patients who should undergo early or more frequent screenings for breast and colorectal cancer.

By following almost 11,000 participants in a national cancer registry for close to a decade, researchers found that family risk profiles changed significantly among adults between the ages of 30 and 50.

The findings, published Wednesday in the Journal of the American Medical Association, suggest that updating the family histories of patients in their 30s and 40s every five to 10 years could save lives, says researcher Sharon Plon, MD, who directs the Baylor College of Medicine Cancer Genetics Clinic.

“Taking a good family history at age 30 will identify a number of high-risk people,” Plon says. “But clearly once is not enough. We found that if we continued to take histories every few years for the next 20 years we would identify even more people at risk.”

Family Cancer Risk Changes With Time

The study participants were registered in the National Cancer Institute’s (NCI) Cancer Genetics Network -- a nationwide population-based registry of people with a personal or family history of cancer.

The cancer status of first- and second-degree relatives, which included parents, siblings, grandparents, aunts, and uncles, were updated during the follow-up.

The analysis revealed that new cancer diagnoses within families were most likely to affect risk assessments and screening recommendations between the ages of 30 and 50.

By following the participants for an average of eight years, the researchers concluded that there was a 5% chance that people in this age group would be newly identified as candidates for early colorectal cancer screening and a 4% chance that women in their 30s and 40s would be newly identified as candidates for aggressive breast cancer screening.

The percentage of participants who met the criteria for high-risk colorectal cancer screening based on family history increased from around 2% at age 30 to 7% by age 50. The percentage of women who qualified for early and more aggressive breast cancer screening increased from around 7% to 11% between the age of 30 and 50.

The merits of prostate cancer screening are the subject of much debate within the medical community. The study found that updating family history did identify men at increased risk for the disease, but the message regarding screening is less clear, Plon says.

Study co-author Diane M. Finkelstein, PhD, says after the age of 50 family history becomes less important because screening is recommended for everyone.

Patients Need to Know 2 Things

The researchers conclude that family cancer history should be updated at least every five to 10 years for patients between the ages of 30 to 50.

Finkelstein says patients who have a first- or second-degree relative with a new cancer diagnosis need to know the answers to two critical questions: "What was the primary site of the cancer?" and "How old was the family member at diagnosis?"

Lenox Hill Hospital Chief of Surgical Oncology Stephanie Bernik, MD, agrees, but she adds that understanding family cancer history may take some detective work given the complicated nature of families today.

“It is not uncommon for patients tell me they don’t know anyone on their father’s side of the family because he really wasn’t in their lives,” she tells WebMD. “I encourage them to get as much information as they can. It is important information to have.”